>>First off, let me address that I think for natives, this is only a good>solution for larger, taller aquaria (which is what Brian was asking>about). I wouldn't go putting a 250 watt halide on a 15 gallon... ;)>With that said, lets discuss heat a little bit...>>The "Heat of Halides", to me, is somewhat of a myth.. I think it's>perpetuated by a couple of things and I'll address each indiviually:>>1) The Raw wattage of the lamp.>2) The wattage per surface area of the lamp.>3) The misunderstanding that the extra UV and IR the halide lamps put>off is "heat".>>The first thing to understand about lighting, with regards to heat is...>"A watt is a watt is a watt." It doesn't matter if it's a standard>flourescent, a pc, halide, an energy saver, high pressure sodium, etc.>It's still a watt, it still has it's own unit of heat associated with>it.>>If you were to put a comparable number of flourescent watts and halide>watts in a heat monitoring device, you'd see the same change in>temperature from both. It's the same heat output. However, this is>where Halide gets it's bad name.... In this experiment, for 175 watts,>you had 6 inches of glass envelope on the halide... And you had over>200 inches of nomal output flourescents to achieve the same wattage!>Extrapolate that out to a 400 watt comparison :)>>As you can see, the heat generated is dispersed over a greater surface>area in flourescents and they don't seem so "hot", which is a certain>misgiving.>>True "Heat" is easy to dispell. If you have an open top tank, you can>just set a regular oscillating fan right on it. A friend of mine put>one of those cheap clip-on fans you can get at Walmat. Evaporation can>dump the temp in an amazing fashion. As well, if you had the halides on>pendants, none of the heat transfer would go to the tank (unless you had>warmed the room).>>I'm stubborn and a purist about halide lighting... I still use enclosed>canopies. I use 4" computer Fans to vent my hoods. However, in my>wanning youth, I'm finding myself to be less of a zealot about it (but>maybe that's a general trend ;). When it heated up last week so early,>I wasn't ready to deal with it, but considering that this is 1500 watts>of ligting over 72x18, I don't think it was any reason to throw the>book out on halide, nor do I think *that* lighting configuration is>anything you would want for native aquaria. I will note tho, I didn't>really have to fuss much with the 175w tanks, and I didn't even have>fans on them (which is getting corrected this weekend ;)>>So that's pretty much a quick triste on heat.>>Now for the fun... The UV and IR. I think this is the single greatest>perpetuator that halide is somehow hotter than flourescents. You stick>your hand underneath a halide lamp, it feels hot right? Is that heat?>>I did a demonstration one time at a friends of ours shop. She has a>greenhouse and uses halide to suppliment the SPS coral and tridacnid>clams which are all photosynthetic critters. We had the good fortune>to have the halides on a pulley system, and big big fan to do the>demonstration.>>"Put your hand under the light, is it "hot"?">"Yes.">"Put your hand down by the water under the light, can you still feel the>heat?" (this is about 2.5' from the halide)>"Yes I can still feel it pretty intensely, but it's not as hot.">(turn the fan on.. wind tunnel ensues)>"Put your hand back under the light, is it "hot"?>"Um. Yeah. A little less, but it's still definately hot.">"Put your hand back down by the water. How comperable is that the first>time?"><everyone 'whoaaaaaa'>>"The same as before!">>I always love seeing shocked faces that look up like "NUHT UH!!!" ;)>>It's this extra energy that comes from the halide lighting that endears>it to those of us who use it to rear photosynthetic organisms. In>arguing the case of those critters I say "They've made a living off the>sun... Why wouldn't I give it to them?" :)>>With that I'll digress a bit and rethink native. I'm not sure if any of>this really plays into your aquaria, if you're using lights to just>make a nice brite aquarium, or if you're interested in rasing plants,>etc but I have some time while doing an import here so I thought I'd>write a bit about it :) I don't think a well planned system you would>have any heat issues. In fact, for anticipating for the heat, I seen a>lot of aquarists drop their tank temps because they got the floro heated>glass off the top, aquired a real gas exchange, began utilizing>evaporation and etc etc. It may actually be intuitive.>>Now there's more that would have to go into just putting new lights on>the tank... There are issues of nutrient conversion that would *have*>to be addressed. You've just given so many new players (algaes) the>ability to step up to the plate, but don't let that scare you. It's>really not all that bad to deal with, and the rewards reciprocate :)>>If you'd like to discuss more, poke around the web a bit and see what>others have to say about lighting. It will probably get overwhelming,>mainly because a lot of people are trying to sell you something and they>don't understand it to begin with. But as you have questions, you can>post them here and I'll try to answer best I can (I'm sure there's other>who have experience with all this too).>>I'll warn you I'm not into the physics side of things, so if we start>getting into Light Theory, I'm going to step away. I like natural>history, and more so, I like watching natural history work. So at times>in those situations (I'll just confess now) I have a tendency to grab my>"Anecdote Ray Gun" and say "Okay Theory Man. Let's see you grow it!">;)>>Todd
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